1. Field of the Invention
The present invention generally relates to liquid flow drainage control in sewage septic tank systems and, more particularly, to an improved drainage pipe flow control comprising a cap insertable from within the distribution box into a projecting end of a drainage pipe and easily adjustable to equalize the drainage of liquid from the box.
2. Description of the Prior Art
Sewage septic tank systems generally comprise a septic or holding tank which receives the raw sewage from a main inlet pipe. A distribution box is connected to receive liquid or effluent discharged from the septic tank. The distribution box is provided with a plurality of outlets at a predetermined distance from the top of the box. These outlets are connected to drainage pipes which are in turn connected to a drainage field. In the drainage field, the drainage pipes are perforated to allow liquid carried by the drainage lines to leach into the surrounding earth. The solids in the raw sewage in the septic tank settle to the bottom of the tank while the liquid or effluent, when it reaches the level of the outlet of the septic tank, flows to the distribution box. From there, the effluent flows through the drainage pipes to the drainage field.
In such sewage septic tank systems, it is necessary for the proper operation of the system and the long life of the drainage field for the discharge into the drainage pipes from the outlets of the distribution box to be absolutely at the same level so that the same flow rate is maintained in each of the drainage pipes. The criticality of this adjustment is due to the slow flow rates of the effluent within a gravity feed system. Precise adjustment to within approximately one sixteenth of an inch or less is desired. The distribution box is typically made of cast concrete and, more recently, of molded plastic. The outlets can be precisely and accurately formed in the mold which is used to cast or mold the box. The problem is one of installation. In spite of the most careful preparation of the hole at the site where the distribution box is to be installed, the box will not be precisely level. As a practical matter, the workmen who routinely install these boxes do not make as careful preparation of the hole as would be desirable, aggravating still further the problem of compensating for the out of level condition of the box so as to provide for an unequalized flow rate of effluent into the drainage pipes. Other factors affecting the flow rate are the grades of each drainage pipe and the soil conditions surrounding the drainage pipe.
When the drainage lines were made of clay tile, it was the procedure to put a trowel of mortar in the openings of the outlets through which the tiles projected. After the mortar dried, the distribution box was filled with water to the level of the outlets. Mortar was then chiseled away as necessary so that the flow out of the outlets was equalized.
With the advent of plastic pipe, such as polyvinylchloride (PVC) and other plastics, designed for septic system drainage fields, the clay tile was no longer used because the plastic pipe was both cheaper and much less fragile. Nevertheless, the problem of equalizing the flow rates remained, but mortar does not adhere well to the plastic pipe. The solution was to form a dam of tar or asphalt in the ends of the drainage pipes and then add or remove tar or asphalt as needed. In other words the tar or asphalt served the same function as the mortar but of course would adhere to the plastic pipe; however, the process in addition to being tedious was quite messy. Another proposed solution was to drill a hole or cut a slot in a standard plastic end cap. The plastic end cap was of the type having a decreasing tape to its inside diameter and intended to make a jam fit over the end of the plastic pipe projecting into the distribution box. The hole or slot in the end cap was off center so that as the end cap was positioned before being jam fit over the end of the pipe projecting into the distribution box, a rough adjustment of the level at which effluent would flow into the drainage line could be made.
One problem with the end cap solution was that for it to function properly, it was necessary for the connection to the drainage line to be sealed. This was accomplished by using a solvent adhesive which "welded" the end cap to the plastic pipe. This could not be applied with water in the distribution box so that after adjustments were made and marked, the box would have to be at least partially drained. Furthermore, if there were any inaccuracies in the marking or installing of the end cap and pipe combinations, there could be no adjustments. The seal to the drainage line was permanent.
If no solvent were used to seal the end cap to the pipe, and reliance were merely placed on the friction jam fit between the pieces for sealing the pieces, rotation of the cap would require loosening before the cap could be readily rotated. This, however, would typically lead to leakage between the end cap and the pipe, and thus make precise rotatable adjustment of flow difficult if not impossible.
Still other proposals have included the use of a special long handled tool or wrench adapted to be inserted into multiple holes drilled in a conventional plastic end cap. However, end caps having multiple holes are not useful at all in certain applications and, moreover, such structure would most likely leak in any event during rotational adjustment. In addition, the forces applied by such a tool or wrench could break the end of the drainage pipe or destroy the seal between the drainage pipe and the distribution box causing the box to leak.
The problems associated with the plastic end cap and pipe combination were partially solved by the device disclosed in U.S. Pat. No. 4,298,470 issued to Billy G. Stallings. Stallings discloses a liquid leveling cap with an eccentric discharge hole in the end face of the cap. The cap fits over the pipe projecting into the distribution box and is rotatable so that the levels of the holes of the several end caps in the distribution box can be precisely adjusted. The Stallings liquid leveling end cap was rotatably secured to the pipe and allowed for relatively freer rotation of the end cap on the pipe to permit adjustment of the liquid levels admitted to the drainage pipes without significant leakage.
Although sanitary regulations adopted by many jurisdictions over the past two decades have required equal flow rates of effluent in the drainage pipes, those working in the field have not fully appreciated these requirements or how to comply with them.